Stock-Based Compensation (Tables)
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12 Months Ended |
Dec. 31, 2016 |
Stock-Based Compensation Expense Related to Common Stock Options, Restricted Common Stock and Common Stock Warrants |
Following is the stock-based compensation expense related to common
stock options, restricted common stock and common stock
warrants:
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Year Ended December 31, |
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2016 |
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2015 |
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Research and development
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$ |
831 |
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$ |
1,018 |
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General and administrative
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1,648 |
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2,382 |
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Total stock-based compensation expense
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$ |
2,479 |
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$ |
3,400 |
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Weighted Average Assumptions Used to Determine Fair Value of Options Granted |
The fair value of the options granted is determined using the
Black-Scholes option-pricing model. The following weighted average
assumptions were used:
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2016 |
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2015 |
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Risk-free interest rate
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1.49 |
% |
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1.65 |
% |
Expected life of the options
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6 years |
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6 years |
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Expected volatility of the underlying stock
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96 |
% |
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101 |
% |
Expected dividend rate
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0 |
% |
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0 |
% |
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Summary of Stock Option Activity |
The following table summarizes the stock option activity in the
stock based compensation plans:
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Number of
Shares |
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Weighted
Average
Exercise
Price |
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Weighted
Average
Remaining
Contractual
Life
(in years) |
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Aggregate
Intrinsic Value
(in thousands) |
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Outstanding, December 31, 2014
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3,332,617 |
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$ |
5.79 |
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Granted
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454,000 |
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3.23 |
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Forfeited/Cancelled
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(348,718 |
) |
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4.42 |
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Exercised
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(95,574 |
) |
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1.80 |
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Outstanding, December 31, 2015
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3,342,325 |
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$ |
5.70 |
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Granted
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1,434,750 |
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0.97 |
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Forfeited/Cancelled
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(120,187 |
) |
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3.41 |
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Exercised
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— |
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— |
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Outstanding, December 31, 2016
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4,656,888 |
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$ |
4.30 |
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6.83 |
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$ |
120 |
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Exercisable, December 31, 2016
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3,384,238 |
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$ |
5.44 |
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5.78 |
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$ |
22 |
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Summary of Additional Information Regarding Outstanding and Exercisable Options under Stock Based Compensation Plans |
The following table summarizes additional information regarding
outstanding and exercisable options under our stock based
compensation plans at December 31, 2016:
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Options Outstanding |
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Options Exercisable |
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Exercise
Price (Range)
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Number of
Shares |
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Weighted
Average
Remaining
Contractual
Life |
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Weighted
Average
Exercise
Price |
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Number of
Shares |
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Weighted
Average
Exercise
Price |
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(in years) |
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$0.87 – 1.00
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1,157,250 |
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9.9 |
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$ |
0.88 |
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206,250 |
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$ |
0.88 |
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$1.37 – 1.83
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341,668 |
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8.2 |
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1.45 |
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197,147 |
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1.51 |
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$2.08 – 2.79
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810,000 |
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6.0 |
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2.28 |
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703,999 |
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2.21 |
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$3.45 – 4.41
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564,517 |
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7.3 |
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3.82 |
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498,712 |
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3.87 |
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$6.24 – 7.56
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1,466,953 |
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4.2 |
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6.99 |
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1,466,953 |
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7.00 |
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$13.38
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316,500 |
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7.0 |
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13.38 |
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311,177 |
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13.38 |
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4,656,888 |
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6.8 |
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$ |
4.30 |
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3,384,238 |
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$ |
5.44 |
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Summary of Restricted Stock Grant Activity |
The following table summarizes the restricted stock grant activity
in the Company’s equity incentive plans from
December 31, 2014 through December 31, 2016:
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Shares |
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Outstanding, December 31, 2014
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416,670 |
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Granted
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337,935 |
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Exercised
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— |
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Options forfeited/cancelled
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— |
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Outstanding, December 31, 2015
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754,605 |
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Granted
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— |
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Exercised
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— |
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Options forfeited/cancelled
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— |
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Outstanding, December 31, 2016
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754,605 |
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